An analytical model for the response of carbon/epoxy-aluminum honeycomb core sandwich structures under quasi-static indentation loading

Abstract

An analytical model is developed to predict the loading and unloading response, as well as the residual dent diameter and dent depth, of carbon/epoxy-aluminum honeycomb core composite sandwich structures undergoing quasi-static indentation loading. The model considers damage created using spherical indenters and is valid up to the barely visible external damage threshold. The initial low load regime (until the onset of core crushing) is modeled using a combination of local Hertzian indentation of an elastic half-space and small deflection plate theory of a circular plate on an elastic foundation. For loads above those required to cause core crushing, the model uses the Rayleigh-Ritz method of energy minimization with the total system energy determined using a combination of face sheet bending energy, face sheet membrane energy and work done to the core during both elastic deformation and crushing. Degraded face sheet properties are used in the model beyond the onset of face sheet delamination, which is predicted using Griffith’s energy criterion. The model is validated using experimental results for sandwich structures consisting of quasi-isotropic 8- (thin) and 16- (thick) ply carbon/epoxy face sheets and aluminum honeycomb cores. The results show that the overall mechanics of the model are fundamentally correct and reflective of physical behavior. Thus, in its present form the model shows promise as a preliminary design tool.

Analytical development on impact behaviour of composite sandwich laminates by differentiated loading regimes

“…( 14), the sign change of the core crushing component would lead to a jump in the force versus indentation relation if the magnitude ξ u is kept constant and equal to ξ max , which contravenes the continuity observed in the experiments. Then, as stated by Singh et al [27], it is considered that, at the beginning of the unloading, the uncrushing region is smaller than the complete crushed area, increasing its dimension as the unloading progresses. In that latter study, it was proposed with great accuracy to experimental results a linear ξ u -P relation as in Eq.…”